cdo/batomorph
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add front/back face detection

Browse Source
This commit is contained in:
Camden Dixie O'Brien
2025-09-23 15:35:26 +01:00
parent 77723aefa0
commit 6eb4da9e06
3 changed files with 26 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
demo.c
View File

@@ -4,6 +4,7 @@
#include "ray.h" #include "ray.h"
#include "vec3.h" #include "vec3.h"
#include <float.h>
#include <limits.h> #include <limits.h>
#include <math.h> #include <math.h>
#include <stdio.h> #include <stdio.h>
@@ -34,7 +35,7 @@ static vec3_t raycol(ray_t ray)
{ {
hit_t hit; hit_t hit;
for (unsigned i = 0; i < NELEMS(scene); ++i) { for (unsigned i = 0; i < NELEMS(scene); ++i) {
if (scene[i].intersect(scene[i].params, ray, &hit)) if (scene[i].intersect(scene[i].params, ray, &hit, 0.0, DBL_MAX))
return vec3_scale(vec3_add(hit.normal, white), 0.5); return vec3_scale(vec3_add(hit.normal, white), 0.5);
} }

11
include/obj.h
View File

@@ -14,6 +14,7 @@
typedef struct { typedef struct {
vec3_t point, normal; vec3_t point, normal;
double t; double t;
bool front;
} hit_t; } hit_t;
typedef struct { typedef struct {
@@ -25,11 +26,17 @@ typedef union {
sphere_params_t sphere; sphere_params_t sphere;
} obj_params_t; } obj_params_t;
typedef bool intersect_fn_t(
obj_params_t params, ray_t ray, hit_t *hit_out, double t_min,
double t_max);
typedef struct { typedef struct {
bool (*intersect)(obj_params_t params, ray_t ray, hit_t *hit_out); intersect_fn_t *intersect;
obj_params_t params; obj_params_t params;
} obj_t; } obj_t;
bool intersect_sphere(obj_params_t params, ray_t ray, hit_t *hit_out); bool intersect_sphere(
obj_params_t params, ray_t ray, hit_t *hit_out, double t_min,
double t_max);
#endif #endif

24
src/obj.c
View File

@@ -2,28 +2,34 @@
#include <math.h> #include <math.h>
bool intersect_sphere(obj_params_t params, ray_t ray, hit_t *hit_out) bool intersect_sphere(
obj_params_t params, ray_t ray, hit_t *hit_out, double t_min,
double t_max)
{ {
const vec3_t centre = params.sphere.centre; const vec3_t centre = params.sphere.centre;
const double r = params.sphere.radius; const double r = params.sphere.radius;
const vec3_t disp = vec3_sub(centre, ray.orig); const vec3_t disp = vec3_sub(centre, ray.orig);
const double a = vec3_dot(ray.dir, ray.dir); const double a = vec3_dot(ray.dir, ray.dir);
const double b = -2.0 * vec3_dot(ray.dir, disp); const double h = vec3_dot(ray.dir, disp);
const double c = vec3_dot(disp, disp) - r * r; const double c = vec3_dot(disp, disp) - r * r;
const double discriminant = b * b - 4 * a * c; const double discriminant = h * h - a * c;
if (discriminant < 0) if (discriminant < 0)
return false; return false;
const double t = (-b - sqrt(discriminant)) / (2.0 * a); const double sqrtd = sqrt(discriminant);
const double low = (h - sqrtd) / a;
const double t = low > t_min ? low : (h + sqrtd) / a;
if (t < t_min || t_max < t)
return false;
const vec3_t point = vec3_add(ray.orig, vec3_scale(ray.dir, t)); const vec3_t point = vec3_add(ray.orig, vec3_scale(ray.dir, t));
const vec3_t normal = vec3_unit(vec3_sub(point, centre)); const vec3_t normal = vec3_unit(vec3_sub(point, centre));
if (hit_out != nullptr) { hit_out->point = point;
hit_out->point = point; hit_out->normal = normal;
hit_out->normal = normal; hit_out->t = t;
hit_out->t = t; hit_out->front = vec3_dot(ray.dir, normal) < 0.0;
}
return true; return true;
} }